China was this morning condemned for its human rights record after a British man who, his supporters say, had mental health problems, was executed for smuggling drugs.

Akmal Shaikh, 53, was put to death at 10.30am local time (2.30am British time) after frantic last-minute pleas for clemency by the Foreign Office failed.

Britain had demonstrated its anger with Beijing over the treatment of Shaikh, who had smuggled 4kg (8.8lb) of heroin into China, when it summoned the Chinese ambassador for a diplomatic dressing down at the Foreign Office.

In what was described as a "full and frank exchange of views", the Foreign Office minister Ivan Lewis asked Fu Ying for clemency and outlined Britain's concern that China had not taken Shaikh's mental health into consideration.

Hours before the deadline – and after voicing Britain's opposition to the death penalty in a telephone call to his Chinese counterpart – Lewis told the ambassador that it was "not right" that Shaikh's mental health had been overlooked by the court that sentenced him.

Speaking after meeting the ambassador, in Britain's 27th representation to China on the case, Lewis said: "China fully understands the strength of feeling in this country and around the world."

But the ambassador made clear that the Chinese judiciary was independent of the government and that the supreme court had made its decision. On Shaikh's mental health, she said all his paperwork had been fed into the judicial process, which had now taken its course.

As MPs lined up to criticise China's action, a spokesman for the embassy said Shaikh had been found with more than 4kg of heroin, and being caught with 50g of heroin was enough for the death penalty under Chinese law.

Downing Street said Britain had done "everything within its power" to secure a fair trial and clemency for Shaikh, who was found guilty of drug smuggling in 2007. "The prime minister has intervened personally on a number of occasions: he has raised the case with Premier Wen [Jiabao], most recently at the Copenhagen summit, and has written several times to President Hu [Jintao]," a spokesman said.

MPs were scathing about China. Ken Purchase, a former Foreign Office ministerial aide and a member of the Commons foreign affairs select committee, called China's actions "absolutely regrettable", adding that the country was trying to position itself in the mainstream of international affairs while persisting with "barbaric actions".

Gisela Stuart, a former Labour minister who also sits on the foreign affairs select committee, said: "When it comes to questions of human rights in China there is still the most enormous gap."

Shaikh was informed of his death sentence yesterday when British consular officials accompanied two of his cousins Soohail Shaikh and Nasir Shaikh, to the secure hospital in Urumqi where he was being held. His death sentence marks the first time an EU national has been executed in China in 50 years.

In a statement after the meeting, they said: "He was obviously very upset on hearing from us of the sentence. We strongly feel that he's not rational and he needs medication. We feel a pardon would allow Akmal to get the medical assistance he needs." The family filed a last-minute petition for a stay of execution and an application for a special pardon to China's supreme court, to the president, and to the standing committee of the people's national congressNational People's Congress orthe parliament.

Shaikh, a father of three, was arrested in Urumqi in September 2007 and charged with drug smuggling. He lost a final appeal last week, but campaigners claim his mental illness was not taken into account.

The anti-death-penalty organisation Reprieve said it had medical evidence that Shaikh believed he was going to China in 2007 to record a hit single that would usher in world peace. It said he was duped into carrying a suitcase packed with heroin on a flight from Tajikistan to Urumqi.

As the hours counted down to his execution, witnesses gave more evidence of Shaikh's strange behaviour in the past.

Paul Newberry, a British national who lives in Poland, described how Shaikh while there had lived in a fantasy world: "He had no money but was never desperate for it. He was clearly not desperate enough to smuggle heroin to China."